The patch titled
Subject: binfmt_elf: document load_bias a little bit
has been added to the -mm tree. Its filename is
binfmt_elf-document-load_bias-a-little-bit.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/binfmt_elf-document-load_bias-a-little-bit.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/binfmt_elf-document-load_bias-a-little-bit.patch
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------------------------------------------------------
From: Rik van Riel <riel@xxxxxxxxxx>
Subject: binfmt_elf: document load_bias a little bit
Patch series "move mmap_area and PIE binaries away from the stack".
There are a few bugs causing the kernel to sometimes map PIE binaries and
the mmap_area where the stack is supposed to go.
This series fixes them for x86, ARM64, and PPC. S390 seems to be ok.
This patch (of 6):
After I and another unnamed developer got confused by the subtraction of
vaddr in this branch of the code, followed by adding vaddr back in a
little bit later, for the third time, maybe it is time to document this
quirky bit of code.
Link: http://lkml.kernel.org/r/20170602152010.2064-2-riel@xxxxxxxxxx
Signed-off-by: Rik van Riel <riel@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Larry Woodman <lwoodman@xxxxxxxxxx>
Cc: Daniel Micay <danielmicay@xxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Florian Weimer <fweimer@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/binfmt_elf.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff -puN fs/binfmt_elf.c~binfmt_elf-document-load_bias-a-little-bit fs/binfmt_elf.c
--- a/fs/binfmt_elf.c~binfmt_elf-document-load_bias-a-little-bit
+++ a/fs/binfmt_elf.c
@@ -930,10 +930,16 @@ static int load_elf_binary(struct linux_
if (loc->elf_ex.e_type == ET_EXEC || load_addr_set) {
elf_flags |= MAP_FIXED;
} else if (loc->elf_ex.e_type == ET_DYN) {
- /* Try and get dynamic programs out of the way of the
+ /*
+ * Try and get dynamic programs out of the way of the
* default mmap base, as well as whatever program they
* might try to exec. This is because the brk will
- * follow the loader, and is not movable. */
+ * follow the loader, and is not movable.
+ *
+ * The load_bias is the difference between the address
+ * in the elf header and the address where the binary
+ * is mmapped.
+ */
load_bias = ELF_ET_DYN_BASE - vaddr;
if (current->flags & PF_RANDOMIZE)
load_bias += arch_mmap_rnd();
_
Patches currently in -mm which might be from riel@xxxxxxxxxx are
binfmt_elf-document-load_bias-a-little-bit.patch
x86-elf-move-32-bit-elf_et_dyn_base-to-256mb.patch
x86-mmap-properly-account-for-stack-randomization-in-mmap_base.patch
arm64-mmap-properly-account-for-stack-randomization-in-mmap_base.patch
arm64-move-compat_elf_et_dyn_base-lower-in-the-address-space.patch
powerpcmmap-properly-account-for-stack-randomization-in-mmap_base.patch
randomstackprotect-introduce-get_random_canary-function.patch
forkrandom-use-get_random_canary-to-set-tsk-stack_canary.patch
x86-ascii-armor-the-x86_64-boot-init-stack-canary.patch
arm64-ascii-armor-the-arm64-boot-init-stack-canary.patch
sh64-ascii-armor-the-sh64-boot-init-stack-canary.patch
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